Dairy Ingredients in Dairy Food Processing 435cream are obtained by changes in the type
and concentration of the ingredients.
Processing of Frozen Desserts
Mix Preparation
In all frozen desserts, processing starts with
standardization of the base and pasteurization
and homogenization. Dairy ingredients are
combined to provide the correct solids and
fat contents. This may occur as a mix of
liquid and dry ingredients. Typically, the
liquid dairy ingredients, water, and liquid
sweeteners are combined and the mix might
be checked for solids and fat. The dry ingre-
dients such as dry dairy powders, sugars,
stabilizers, emulsifi ers, and cocoa powder are
added to the liquids through a blender, either
in - line through a tri - blender, or through recir-
culation through an agitated tank. In some
cases, a pre - blend of dry ingredients is made
with sugar to ensure that the stabilizers can
be incorporated without forming “ fi sh eyes, ”
which can clog in - line strainers. Some ingre-
dients that are diffi cult to solubilize may need
to be pre - heated in water and added as a
slurry to the mix.
Because of the amount of stabilizer in the
mix, it is important to not incorporate too
much air during the blending stage and
causing foam. Problems are encountered
with pasteurization by continuous pasteuriza-
tion systems if there is excess foam because
the foam may not be able to be pumped, there
is burn - on in the plates, and tank volume
meters are affected by the less - dense foam.
Bases are usually processed as a “ white
base, ” which is simply sweetened and ready
for fl avor addition post - pasteurization, and a
“ chocolate base, ” which has had the cocoa
powder added but no fl avors. When products
are pasteurized in small batches through a
batch pasteurizer, or when large volumes of
a dry ingredient system include the fl avor
(such as eggnog), the fl avors might be added
during blending and prior to pasteurization.
Pasteurization
The main purpose of pasteurization is to
ensure the safety of the product and destroy
any pathogenic organisms. Because of the
high solids levels, the temperature require-
ments to achieve safe products are higher
than those for fl uid milk (Figure 17.1 ). The
heat treatment at this step also contributes a
cooked fl avor to the mix, increases the vis-
cosity by denaturing proteins, and incorpo-
rates ingredients and affects their functionality
(especially emulsifi ers and stabilizers). The
heat also melts the milk fat so that it is in a
liquid state when it is homogenized, resulting
in homogenization effi ciency.Homogenization
Homogenization of the mix occurs immedi-
ately after pasteurization while the base is
still hot in the case of batch pasteuriza-
tion, or after pre - heating the base during
continuous pasteurization. Homogenization
completes the mixing of ingredients, reduces
fat globule size, further denatures proteins
to improve water binding, and aids in the
formation of new “ membrane ” material sur-
rounding the fat (comprised of proteins
and added emulsifi ers). In milk, the reduc-
tion in fat globule size is intended to pre-
vent the fat from rising to the top of the
liquid. In addition, if the mix is not homog-
enized, the ice cream can have a churned
defect, evidenced by greasy butter on the
blades of the freezer and greasiness of the ice
cream.
When homogenized on a two - stage
homogenizer, 17.2 MPa (2,500 psi) is typical
(14 MPa [2,000 psi] fi rst - stage, 3.5 MPa [500
psi] second stage) for mixes under 14% fat.
Mixes with a fat content over 14% have
lower homogenization pressures to prevent
excessive mix viscosity (Marshall et al.,
2003 ). Products intended for soft - serve appli-
cations are packaged at this point. Frozen
yogurt manufacturing also has the addition of
culture prior to packaging or proceeding to